1. Field of the Invention
The present invention relates to a plasma processing apparatus which can be used to effect processes such as to plasma chemical vapor deposition and plasma dry etching.
2. Description of the Related Art
In a previous plasma processing apparatus, a lower plate electrode and an upper plate electrode are spaced apart within a chamber, and a workpiece is placed on the lower electrode. For example, the upper electrode is connected to a high frequency electric power source while the lower electrode is connected to ground. Reaction gas is introduced into the chamber via a gas feed pipe, while the chamber is evacuated via an evacuation pipe. The upper plate electrode can be raised or lowered by a lifting device. The upper plate electrode is moved to control the distance between the lower plate electrode and the upper plate electrode according to optimum plasma processing conditions. However, during plasma processing the processing conditions may vary. For example, when a multi-layer film is formed on the surface of a workpiece, processing conditions are changed for each layer. As another example, after a workpiece is first treated at a high etching rate, the workpiece can be dry-etched at a low etching rate to secure the homogeneity of the surface. In such cases, the gas flow and plasma discharge cannot be optimized in each processing step because only the upper plate electrode can be moved.
Further, an ion assist effect is exerted only in the direction of one of the plate electrodes upon cleaning the inside of the chamber, so that cleaning of the entire inside of the chamber cannot be rapidly performed.